Purification of tar acid-bearing oils



Patented Ap 7, 1931 I UNITED STATES PATENT OFFICE SOLOMON CAPLAN, OFBROOKLYN, NEW YORK, ASSIGNOR TO COMBUSTION UTILITIES Nd Drawing.

in bearing oils containing them.

Some tar acid-bearing oils (such as low temperature tars, blast furnacetars, vertical retort tars, shale oils and other liquid condensatesresulting from the distillation of 1 bituminous material undercarbonizing conditions mild enough to preserve the liquid by-products ina substantially primary and undecomposed form) contain certain impuritites which render them unsatisfactory or make them undesirable forcertain uses.

One form in which these impurities manifest themselves is in theproduction of colored compounds when such oils are used for themanufacture of disinfectants, animal dips,

2o saponified cresol or tar acid solutions and related products. Afterexhaustive and thorough investigation of the chemical compositions andproperties of these colored compounds their origin has been traced tocertain strongly reducing ortho-dihydric tar acids, similar to but notincluding catechol. Thus one of these bodies has been isolated andidentified as a new homologue of catechol comprising 3, 4- or 3,6-dimethy1 catechol.

The primary object of the present invention is to provide a process forremoving color producing compounds of the type referred to from taracid-bearing oils containin them.

eretofore in pr'eparin and refining tar acid-bearing oils of the c assdescribed for use in the manufacture of disinfectants, animal dips andsimilar products, the oils have been subjected to washing treatmentswith aqueous sodium carbonate solutions. This treatment, however, failsto give even approximately complete removal of the color forming matterexcept with oils which contain unusually small amounts of such. colorproducing bodies. In treating other tar acid-bearing oils, washing withdilute caustic soda solution has been employed, but this treatmentinvolves a very considerable loss of the desirable tar acids of highgermicidal CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF MAINEPURIFICATION OF TAR ACID-BEARING OILS Application filed September 25,1926. Serial No. 137,825.

value,.which are extracted together with the color-forming materials bythe caustic soda treatment. Another method has been recently proposedfor removing these color producing compounds from coal tar distillatesand the like, which comprises washing the olls with aqueous solutions ofweakly alkaline buffer agents such as calcium hydrox- 1de an ammonium hdroxide. While this latter method of treating the oils has proven muchmore satisfactory than methods now in use 1n the trade, it has beenfound that the action of the alkaline bufier agents is often incompletein the case of tar acid-bearing 0118 containing appreciably largequantities of color-producing matter. Fractionation of the oil withrejection of the portion boiling above 230 C. has also been advocated,but since this excludes the larger portion of the 011, mcluding most ofthe high boiling tar acids which are the most valuable germicidespresent in the oil, the method is not commerically feasible.

Another object of the present invention is to provide a process by whichthe color-producing bodies present in such tar acid-bearing oils can becheaply and completely extragted without also removing valuable tar ac1s.

The most satisfactory methods heretofore suggested and employed forremoving colorproducing compounds from tar acid-bearing oils containingthem have involved the use of chemical reagents or solvents for washingout the color-producing bodies. Any washing method for effecting theremoval of impurities is inherently inadvantageous in that it involvesthe introduction of an additional or supplementary step in the regularrefining operation, as well as additional equipment in the form oftanks, pumps and piping.

One feature of the present invention contemplates treating taracid-bearing oils of the class described to remove color-producingcompounds therefrom as a part of the regular routine refining treatmentto which the oils are commonly subjected, and without the use ofadditional operating steps or expensive equipment.

With these and other objects and features in view the invention consistsin the method of purifying tar acid-containing oils hercinafterdescribed and particularly defined in the claims.

Essentially thc'mcthod of purifying taracid-bearing oils forming thesubject of the present invention. in its preferred form, consists indistilling the oil in the presence of non-acidic ferric compounds suchas the hydroxide, basic acetate, boratc, phosphate, stearate, oleate andthe like, and collecting the distillate freed from the impuritiesremoved by chemical combination with such non-acidic ferric compounds.It has been found that ferric compounds which are nonacidic in characterappear to act as oxidizing agents. converting the orthodihydric tar acidimpurities into black, water-insoluble compounds which are non-volatile,thus permitting the recovery by distillation of a distillatesubstantially free of such color-forn'ling bodies. By this method oftreatment no additional operation or equipment not commonly employed intreating the tar acid-bearing oils is required, and practically none ofthe desirable and valuable monohydroxy tar acids of high germicidalvalue are lost from the purified distillate.

The following procedure has proven satisfactory in treating a tardistillate having a boiling range of from 190-330 C. and containingabout 30% valuable tar acid bodies, said tar distillate having beenproduced by the distillation of a commercial low te1nperature tar. Thetar oil was distilled to a vapor temperature of about 330 C. afteradding thereto 5% of the weight of the tar oil of ferric stearate, and adistillate was obtained which, when made up into a disinfectantemulsion, was neither red nor pink in color. The particular tar oil thustreated contained much more of the color-forming impurities than isusually encountered in tar refining practice. Obviously tar acid-bearingoils containing less color-forming matter (orthodihydric tar acids) thanthe one cited can be purified with correspondingly less of the ferricsoap. Experiments have shown that ferric chlorid when added to the tarprior to distillation is not a satisfactory reagent for converting thecolor-producing bodies into insoluble matter, apparently because of itsacid reaction. Ferric soaps, such as stearate and oleate, on the otherhand have no acid reaction, and possess the additional characteristic ofbeing readily soluble in the acid-bearing oils under treatment, so thatthey are particularly well suited for this purpose. As indicated aboveother non-acid ferric compounds, such as hydroxide, basic acetate,borate and phosphate may be used, and although they are less soluble inthe acid-bearing oils than the ferric soaps, their use is oftenpreferred because they are less expensive. In using flux column mountedat the head of the distillation still, rather than to add them directlyto the tar or tar oil in the still. Thus it has been found that anentirely satisfactory purification can be carried out when the nonacidicferric treating agent is supported in a reflux column on porous materialsuch as coke, pumice and the like, during the distillation of the taracid-bearing oils in the underlying still.

It is not intended to limit the scope of the present invention to thetreatment of oils containing a definite percentage of colorforming andnon-color-forming compounds, nor to the use of definite proportions ofpurifying agents, nor to the employment of particular temperatures orother particular conditions of distillation. The process is particularlyapplicable to the preliminary distillation to soft pitch of a tar oilcontaining tar acid bodies admixed with hydrocarbon oils, but it is notlimited to the treatment of such oils and may be applied to thesecondary distillation of tar acid-bearing distillates recovered in apreliminary distillation.

B y employing the process forming the subject-matter of the presentinvention for the purification of tar acid-bearing oils, disinfectantemulsions can be prepared from soap base blends of the distillate whichwill not turn pink, and the purification of the oil can be completed ata relatively small additional expense over that normally incurred intreating similar oils in which the color-producing impurities are notencountered, without materially lowering the value of the disinfectantand germicidal agents prepared therefrom. i

The term tar-acid-bearing oil is used in the description and claims todefine coal tars and all oils derived from such tars, as Well as shaleoils. The tar acid content of coal tars, particularly those of lowtemperature origin, may often consist almost entirely of compoundswhich, while they resemble the phenols or tar acids of coke oven tar insome of their properties, do not come within the generally accepteddefinition of a phenol but are rather hydroxyl derivatives of cyclichydrocarbons which are non-aromatic in character, having hydrogen andalkyl side chains attached to the nucleus.

The preferred form of the invention having been thus described, what isclaimed as new is:

1. A method of treating tar acid-bearing oils to remove color-producingbodies therefrom which comprises distilllng the oil in contact with anon-acidic ferric compound, and collecting the purified distillate. I

2. A method of eliminatin color-producing compounds from taracid-bearing oils containing them which comprises distilling the oil incontact with an amount of nonacidic'ferric compoud suflicient totransform all the color-producing bodies into non-vola tile compoundswhich will not pass over with the distillate.

3. A method of removing color-producing compounds from tar acid-bearingoils containing them which comprises distilling the oil, passing thedistillation vapors through a reflux column containing a non-acidicferric compound as a filling, and condensing the purified distillationvapors after they have passed the reflux column.

4. A method of removing color-producing impurities from tar acid-bearingoils containing them which comprises distilling the oil, passing thedistillation vapors through a reflux column containing a porous fillingimpregnated or coated with a non-acidic ferric compound, and condensingand separately collecting the purified distlllate.

5. A method of removin color-producing compounds from tar acidearingoils containing them which comprises admixing with the oil a non-acidicferric compound soluble therein, subjecting the mixture to distillation,and condensing and separately collecting the purified distillate.

3 6. A method of treating tar acid bearing oils to removecolor-producing bodies therefrom which comprises the steps of distillingthe oil, refluxing the vaporized oil, and condensing the said vaporizedoil and, during one of the steps prior to the condensation of the oil,contacting the latter with a nonacidic ferric compound. In testimonywhereof I afiix m signature.

. SOLOMON APLAN.

